Denis, Updates are always queued on primary nodes when write-behind is enabled, regardless of atomicity mode. This is required because otherwise updates can be written to the database in a wrong order.
We did not queue database updates on backups because we did not have a mechanism that would allow us to track which updates have been written to the database and which are not. Now that we have a partition counter that is already used in continuous queries failover, it can also be reused for write-behind ACKs. I thought we had a ticket for this. I will re-check if this is true, and will create if it is not there yet.
